In our U.S. application Ser. No. 597,217 there was disclosed a process and apparatus for separating as a solid from a (screened) contaminated polar liquid such as water, dissolved and/or suspended particles, thus obtaining (a) essentially pure liquid (e.g. water) and (b) sterile sludge. In some instances, desired ingredients, such as precious metals, were recoverable from the sludge by fractionation. Typical feed stocks were municipal sewage and/or industrial/agriculture waste water. The apparatus consisted of sequentially flow-connected units comprising (a) an aerating and macerating collection tank (surge tank), (b) an acidifying chamber into which SO.sub.2 is metered and mixed, (c) a submerged-iron-bed containing tank which (in response to flow through of the acidic media) furnishes ferric/ferrous ions for oxidative reaction with the flow stream, (d) means for controlled admixture of air and alkaline reagent (e.g. NaOH or Ca(OH).sub.2) into the stream, (e) flocculation and solids-separation means including pH control. Each segment of the monitored and flow-controlled stream would be retained in each successive unit for the required reaction/treatment time, and then flowed to the next unit; thus when all segments of the stream were stepped forward simultaneously, the residence time in each unit was essentially the same, namely it was the longest reaction time required in any unit if some were unequal.
However the treatment pattern exhibited some points of weakness when restricted to use of that apparatus. Thus, if the flow had to be suspended for correction of a local factor at any particular point along the line, the entire flow necessarily stopped. This could result in reestablishment in the subsequent flow of some organisms (often reintroduced from the air) which had earlier been knocked out of the stream by the initial acid treatment step. The composite procedure which uses successive treatment by strong acid and then by strong alkali ensures elimination of all micro-organisms; those not eliminated by one reagent are eliminated by the other. However when the two extremes of pH occur at opposite ends of a relatively long intermediate procedure, the problem of reinfection from apparatus which is subsequent to initial acid-treatment units also increases. Other apparatus problems include sediment buildup on the walls and lime encrustation of conduits and valves. These can be combatted by acid treatment if promoted by alkali.
Also, a scheduled flow procedure desirably should be adaptable so as to accommodate the differences in feed stocks. For example, proteins denature and float or settle fairly rapidly in acid media and should be promptly removed substantially as formed (rather than carried through to the final alkaline separation). This might require a structural by-pass or alternate flow, if such a permanent pattern were not desired.
Alternately, colloidal material associated with oil and grease (e.g. refinery waste stream; laundry or car wash effluent; etc.) may require variations of procedure such as flow rate, residence time, pH, etc. directed to the particular contaminant and/or its specific state (such as emulsive). Also, particular flocculants may show greater adherance to the iron bed or chamber walls of the apparatus which therefor have to be flushed down oftener or with stronger reagents. In brief, even though successive sub-units are assembled in a permanent flow stream or "assembly line", at times it is highly desirable to be able to treat one or the other as an independently adjustable unit while the others are still left to function as parts of the whole.
The basic process detailed in our Ser. No. 597,217 may be summarized as a stepwise treatment of flowable polar liquid such as water, which liquid contains dissolved and/or suspended contaminants. At least a minimum (0.1% wt. ) of total solid contaminant should be capable of accepting a galvanic charge, which minimum quantity may be added if not initially present. All particulate matter present should have a size in the range of about 30 to about 225 microns diameter, free surface energy of about 100 to about 500 ergs/cm.sup.2 and density of about 1.05 to about 2.0 g/cm.sup.3. That is, gross solids are initially removed as by screening and the remainder are reduced to this particle size to which a galvanic charge is then imparted by pH control of the liquid medium which is held or flowed in electrically insulated apparatus. The body of liquid is moved stepwise through successive reaction units and connecting flow channels which are constructed in accordance with specific dimensionless parameters so as to avoid undesired coalescence (precipitation) of the moving, charged particles.
The body of liquid is first exposed to a strong acidic oxidizing environment of about pH 2.0 to about 2.5 produced by admixture therewith of sulfur dioxide, air and free electrons/ions derived from a flow-through bed of pieces of iron. With continued intermixing of air or oxygen, the body of liquid is then made strongly alkaline by addition of lime or sodium hydroxide at pH about 8 to about 11. Desirably with electrically grounding the liquid, ferric hydroxide is flocculated and carries down other contaminants with it. The resulting sterile sludge and supernatent liquid (decontaminated water) can be further processed if desired, by dehydrating and fractionating the former, and filtration plus incorporation of oxygen into the latter.
The present apparatus provides a more effective means of carrying out such basic process by coupling the present conic reaction chamber with commercially available handling and control units to form a complete flow apparatus, which may even be automated.